Programmable logic devices (PLDs) are a well-known type of integrated circuit that can be programmed to perform specified logic functions. One type of PLD, the field programmable gate array (FPGA), typically includes an array of programmable tiles. These programmable tiles can include, for example, input/output blocks (IOBs), configurable logic blocks (CLBs), dedicated random access memory blocks (BRAM), multipliers, digital signal processing blocks (DSPs), processors, clock managers, delay lock loops (DLLs), and so forth.
Each programmable tile typically includes both programmable interconnect and programmable logic. The programmable interconnect typically includes a large number of interconnect lines of varying lengths interconnected by programmable interconnect points (PIPs). The programmable logic implements the logic of a user-design using programmable elements that can include, for example, function generators, registers, arithmetic logic, and so forth.
The programmable interconnect and programmable logic are typically programmed by loading a stream of configuration data into internal configuration memory cells that define how the programmable elements are configured. The configuration data can be read from memory (e.g., from an external PROM) or written into the FPGA by an external device. The collective states of the individual memory cells then determine the function of the FPGA.
Another type of PLD is the Complex Programmable Logic Device, or CPLD. A CPLD includes two or more “function blocks” connected together and to input/output (I/O) resources by an interconnect switch matrix. Each function block of the CPLD includes a two-level AND/OR structure similar to those used in Programmable Logic Arrays (PLAs) and Programmable Array Logic (PAL) devices. In some CPLDs, configuration data is stored on-chip in non-volatile memory. In other CPLDs, configuration data is stored on-chip in non-volatile memory, then downloaded to volatile memory as part of an initial configuration sequence.
For all of these programmable logic devices (PLDs), the functionality of the device is controlled by data bits provided to the device for that purpose. The data bits can be stored in volatile memory (e.g., static memory cells, as in FPGAs and some CPLDs), in non-volatile memory (e.g., FLASH memory, as in some CPLDs), or in any other type of memory cell.
The terms “PLD” and “programmable logic device” include but are not limited to these exemplary devices, as well as encompassing devices that are only partially programmable.
To enhance functionality of PLDs, embedded cores have been added. For example, FPGAs may include one or more hardwired microprocessors. However, an Ethernet Media Access Controller (“EMAC”) core for PLDs has only been available as a program core. For example, a program or “soft” implementation in FPGA programmable circuitry (“fabric”) of an EMAC is available from Xilinx, Inc. of San Jose, Calif., which is described in additional detail in “1-Gigabit Ethernet MAC Core with PCS/PMA Sublayers (1000BASE-X) or GMII v4.0” by Xilinx, Inc. [online] (Aug. 25, 2004) <URL:http://www.xilinx.com/ipcenter/catalog/logicore/docs/gig_eth_mac.pdf>, which is incorporated by reference herein in its entirety (hereinafter “soft EMAC core”).
Advantageously, having a soft EMAC core allows users to connect an FPGA to a network, such as an Ethernet. Unfortunately, the cost of the soft EMAC core implementation is significant with respect to use of configurable logic cells.
Accordingly, it would be desirable and useful to provide an EMAC core that uses fewer configurable logic cells than a soft EMAC core and provides the same or greater functionality of a soft EMAC core. Moreover, such an EMAC core may be substantially compatible with the Institute of Electronic and Electrical Engineers (“IEEE”) specification 802.3-2002. Furthermore, as PLDs may have any user instantiated design, such an EMAC core may be independent of user design.